SERUM CONCENTRATIONS OF BISNORBIOTIN AND BIOTIN SULFOXIDE INCREASE DURING BOTH ACUTE AND CHRONIC BIOTIN SUPPLEMENTATION

In addition to the pharmacokinetic interest, serum concentrations of b iotin and biotin metabolites are important because biotin in serum mig ht interfere with assays that use avidin-biotin detection systems. Wit h acute and chronic oral administration of biotin the serum concentrat ion of biotin increases. Because of limited specificity of bioassays o r avidin-binding assays used in previous studies, the proportion of th e increase attributable to biotin metabolites (if any) remains unknown . To address these questions 15 adults consumed 1,200 mu g biotin dail y for 14 days. Blood samples were obtained before biotin ingestion and at 3 hours after biotin ingestion on the first day (''acute supplemen tation'') and the fourteenth day (''chronic supplementation''). Biotin , bisnorbiotin, and biotin sulfoxide were measured with a chemically s pecific high-pressure liquid chromatography/avidin-binding assay. Seru m concentrations of biotin, bisnorbiotin, and biotin sulfoxide increas ed approximately fiftyfold with acute supplementation of biotin; each increased further with chronic supplementation. With acute supplementa tion the proportion of the total attributable to metabolites did not d ecrease significantly, suggesting that pathways for biotin catabolism are not easily saturated. With chronic supplementation the proportion of the total attributable to metabolites did not increase significantl y, suggesting that biotin catabolism was not substantially induced. We conclude that on a mole basis the contribution of biotin metabolites is important, and we provide an estimate of the biotin and biotin meta bolite concentration that might be encountered in individuals who self -select large biotin supplements.